A prospective program is being instituted in Santo Domingo to determine whether maternal dengue antibodies prejudice the health of infants, who are infected with dengue viruses during the first eight months of life. To date 347 cord-maternal serum pairs and 46 four-month infant serum specimens have been collected and 218 cord-maternal pairs and all the four month sera were tested for dengue 2 and 3 hemagglutination-inhibition (HI) antibodies. Eighty-nine percent of the maternal sera contained dengue 2 antibodies, while 74% had dengue 3 antibodies. Seventy-seven cord sera had higher HI dengue 2 and 3 titers than the titers in their corresponding maternal counterparts. Thirty had lower cord titers. However, all except one infant lost most of their HI titer by 4 months, suggesting that by this time most infants were again susceptible to dengue infections. Twenty-eight infants were considered under weight at birth, and six percent (5/84) had elevated IgM concentrations. IgM dengue antibody evaluations are being made on these specimens to identify in utero dengue infections.